3 Answers

po304 is radom misfire # 4 cylinder, not 100% positive, check plug's and wires if you havn't change them in while, put new ones on. Next tank full put 1 can of Seafoam in to clean injectors, if it run,s better you got dirty injectors.

P0115 is engine coolant sensor, go to www.obdcodes.com, check out solutions, good luck. My kid has a 1992 Sentra runs like a top , rust bucket, tornado chaser, bad syncro between 3 and 4 gear, but it's a keeper.

Could have head gasket problem's, cause you said it start's but then it start's runnig funny, and quit's. Pull oil dip stick out if oil look's creamy,you got oil and coolant together, major problem and moola to mechanic. Need a head job.